我正在创建一个具有诸如Product,Category,Mechanical,UsageLocation等实体的Spring Boot应用程序。所有这些实体的共同点是它们都具有一个名为name的String属性,并且可以使用name从UI进行过滤。我已经写了一个使用名称过滤产品的规范,它正在起作用。下面是代码
public final class ProductSpecifications
{
public static Specification<Product> whereNameContains(String name)
{
Specification<Product> finalSpec = (Root<Product> root, CriteriaQuery<?> query, CriteriaBuilder cb)
-> cb.like(root.get(Product_.PRODUCT_NAME), "%"+name+"%");
return finalSpec;
}
public static Specification<Product> whereNameEqauls(String name)
{
Specification<Product> finalSpec = (Root<Product> root, CriteriaQuery<?> query, CriteriaBuilder cb)
-> cb.equal(root.get(Product_.PRODUCT_NAME), name);
return finalSpec;
}
}
现在的问题是,我不得不再次编写相同的代码来过滤其他实体,唯一的区别是类名(产品),字段名(PRODUCT_NAME)和方法的返回类型。我可以创建一个通用的类和方法,将类名和字段名作为参数传递给它,并返回各自返回类型的说明。
SpecificationsBuilder
通用@Service
public final class SpecificationsBuilder<T>
{
public static Specification<T> whereNameContains(String key,String name)
{
Specification<T> finalSpec = (Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb)
-> cb.like(root.get(key), "%"+name+"%");
return finalSpec;
}
}
然后进入控制器@AutowireSpecificationsBuilder
@Autowire private final SpecificationBuilder<Product> specificationBuilder; public List<Product> getAll(String name) { Specification<Product> specification = specificationBuilder.whereNameContains(Product_.PRODUCT_NAME, name); List<Product> products = productRepo.findAll(specification);// pass the specifications return products; }
您可以为SpecificationBuilder创建自己的通用库,我有一个。您可以找到详细信息here
import java.util.List;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
import com.ec.application.model.Product;
import com.ec.common.Filters.FilterAttributeData;
import com.ec.common.Filters.FilterDataList;
public class SpecificationsBuilder<T>
{
//#######################################/#################//
// Level 0 - If the field that you want to query is parent entity //
//########################################################//
public Specification<T> whereDirectFieldContains(String key,List<String> names)
{
Specification<T> finalSpec = null;
for(String name:names)
{
Specification<T> internalSpec = (Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb)
-> cb.like(root.get(key), "%"+ name +"%");
finalSpec = specOrCondition(finalSpec,internalSpec); // to append specifications as I am filtering based on list of strings
}
return finalSpec;
}
//#######################################//
// Level 1 - If you want to query a child entity. // //
//#######################################//
public Specification<T> whereChildFieldContains(String childTable, String childFiledName,
List<String> names)
{
Specification<T> finalSpec = null;
for(String name:names)
{
Specification<T> internalSpec = (Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb)
-> cb.like(root.get(childTable).get(childFiledName), "%"+ name +"%");
finalSpec = specOrCondition(finalSpec,internalSpec); // to append specifications as I am filtering based on list of strings
}
return finalSpec;
}
//#######################################//
// Reusable Spec Setter to handle NULLs. //
//#######################################//
public Specification<T> specAndCondition(Specification<T> finalSpec, Specification<T> internalSpec)
{
if(finalSpec == null) return internalSpec;
else return finalSpec.and(internalSpec);
}
public Specification<T> specOrCondition(Specification<T> finalSpec, Specification<T> internalSpec)
{
if(finalSpec == null) return internalSpec;
else return finalSpec.or(internalSpec);
}
}
这是实体规范类的代码
public static Specification<Product> getSpecification(FilterDataList filterDataList) { List<String> productNames = specbldr.fetchValueFromFilterList(filterDataList,"product"); List<String> categoryNames = specbldr.fetchValueFromFilterList(filterDataList,"category"); Specification<Product> finalSpec = null; if(productNames != null && productNames.size()>0) finalSpec = specbldr.specAndCondition(finalSpec, specbldr.whereDirectFieldContains(Product_.PRODUCT_NAME, productNames)); if(categoryNames != null && categoryNames.size()>0) { finalSpec = specbldr.specAndCondition(finalSpec, specbldr.whereChildFieldContains(Product_.CATEGORY,Category_.CATEGORY_NAME, categoryNames)); } return finalSpec; }